AFMカンチレバーの振動特性に及ぼす空気膜スクイズ反力と表面間力の影響

抄録

Atomic force microscope (AFM) has been widely used to evaluate the surface interaction between two surfaces in micro/nanoscale, and they are measured by the deflection of the cantilever at the end by the optical lever method. Because the optical lever method measures the deflection of the cantilever by its deflection angle, a measurement error occurs between them. To fix the error, analyses on the vibration characteristics of the cantilever are necessary. In this study, vibration characteristics of AFM optical cantilever with surface forces acting on the tip were analyzed. Surface forces were introduced by assuming a spring and damping acting at the end of the cantilever. The vibration characteristics of the cantilever were analyzed by solving the equation of motion with various spring constants and damping coefficients. Furthermore, the air film squeeze force was derived from the molecular gas-film lubrication (MGL) equation, and vibration analysis was performed considering the case where the air film squeeze force and van der Waals force act as surface forces. They were introduced into the equation in the form of the spring constant and the damping coefficient. In the result, the amplitude ratio and the phase shift derived from the optical lever method were shown with respect to the curvature radius of the cantilever tip.